1. Field of the Invention
The present invention relates to a switch open-close state-detecting circuit, particularly to a switch open-close state-detecting circuit which detects a change of a state in a plurality of switches either from a closed state to an open state or from the open state to the closed state to make it possible to control the operation modes of a controller with a detected output.
2. Description of the Related Art
In various control apparatuses with a controller consisted with a microcomputer, such as, for example, automotive control apparatuses mounted in an automobile, it is typical that the operation mode of the controller is automatically shifted from the normal mode to the sleep mode with small power consumption to suppress needless power consumption in the controller, when a predetermined time passed after the control apparatus comes into the non-working condition and all of the plurality of operating switches are shifted into the non-controlling state.
On the other hand, to return the controller operation mode from the sleep mode to the normal mode, it is required to supply an interrupt signal to a control terminal of the controller and this interrupt signal is produced with a switch open-close state-detecting circuit. Namely, the switch open-close state-detecting circuit detects that any one of a plurality of switches is operated and the operated switch is shifted from the non-controlling state to the controlling state to generate the interrupt signal, or example, for changing from the high level state to the low level state to supply it to the control terminal of the controller to return the controller operation mode from the sleep mode to the normal mode.
FIG. 3 is a circuit diagram illustrating an example of a construction of a known switch open-close state-detecting circuit and a circuit surrounding it, which is used in an automotive controlling apparatus.
As shown in FIG. 3, a circuit portion which includes the switch open-close state-detecting circuit 40 comprises a plurality (having n units) of manually operated switches 31.sub.1, 31.sub.2, 31.sub.3, . . . , 31.sub.(n-1), 31.sub.n, a controller 32 including at least n units of input terminals I.sub.1, I.sub.2, I.sub.3, . . . , I.sub.(n-1), I.sub.n and a control terminal I.sub.c, a resistor 33.sub.1 and a diode 34.sub.1 connected in series between the switch 31.sub.1 and the input terminal I.sub.1, a resistor 33.sub.2 and a diode 34.sub.2 connected in series between the switch 31.sub.2 and the input terminal I.sub.2, a resistor 33.sub.3 and a diode 34.sub.3 connected in series between the switch 31.sub.3 and the input terminal I.sub.3, . . . , a resistor 33.sub.(n-1) and a diode 34.sub.(n-1) connected in series between the switch 31.sub.(n-1) and the input terminal I.sub.(n-1), a resistor 33.sub.n and a diode 34.sub.n connected in series between the switch 31.sub.n and the input terminal I.sub.n, a capacitor 35.sub.1 connected between the node of the resistor 33.sub.1 and the diode 34.sub.1 and a grounding point, a capacitor 35.sub.2 connected between the node of the resistor 33.sub.2 and the diode 34.sub.2 and a grounding point, a capacitor 35.sub.3 connected between the node of the resistor 33.sub.3 and the diode 34.sub.3 and a grounding point, . . . , a capacitor 35.sub.(n-1) connected between the node of the resistor 33.sub.(n-1) and the diode 34.sub.(n-1) and a grounding point, a capacitor 35.sub.n connected between the node of the resistor 33.sub.n and the diode 34.sub.n and a grounding point, a power supplying resistor 36.sub.1 connected in series along with a detecting resistor 41 to be described later between the switch 31.sub.1 and a power source V.sub.cc, a power supplying resistor 36.sub.2 connected in series along with a detecting resistor 41 to be described later below between the switch 31.sub.2 and the power source V.sub.cc, a power supplying resistor 36.sub.3 connected between the switch 31.sub.3 and the power source V.sub.cc, . . . , a power supplying resistor 36.sub.(n-1) connected between the switch 31.sub.(n-1) and the power source V.sub.cc, a power supplying resistor 36.sub.n connected between the switch 31.sub.n and the power source V.sub.cc, a power supplying resistor 37.sub.1 connected between the input terminal I.sub.1 and a power source V.sub.dd, a power supplying resistor 37.sub.2 connected between the input terminal I.sub.2 and the power source V.sub.dd, a power supplying resistor 37.sub.3 connected between the input terminal I.sub.3 and the power source V.sub.dd, . . . , a power supplying resistor 37.sub.(n-1) connected between the input terminal I.sub.(n-1) and the power source V.sub.dd, and a power supplying resistor 37.sub.n connected between the input terminal I.sub.n and the power source V.sub.dd.
Also, the switch open-close state detecting circuit 40 comprises a detecting resistor 41, a capacitor 42 and a diode 43 connected in parallel between the resistor 36.sub.1 (and the resistor 36.sub.2) and the power source V.sub.cc, the first inverter 44 and the second inverter 45 cascade-connected between the node of a resistor 36.sub.1 and the detecting resistor 41 and the control terminal I.sub.c, a capacitor 46 connected between the output of the first inverter 44 and a grounding point and a power supplying resistor 47 connected between the control terminal I.sub.c and the source V.sub.dd.
The circuit portion including the switch open-close state-detecting circuit 40 in accordance with the above mentioned construction generally works as described below;
In the normal mode of the operation modes of the controller 32, when the switch 31.sub.1 is in the open state, the source voltage of V.sub.cc is applied to the cathode of the diode 34.sub.1 via the detecting resistor 41, the power supplying resistor 36.sub.1, and the resistor 33.sub.1. On the other hand, since the source voltage of V.sub.dd is applied to the anode of the diode 34.sub.1 via the power supplying resistor 37.sub.1, the source voltage of V.sub.dd is supplied to the input terminal I.sub.1 of the controller 32 as a high level voltage. At this time the controller 32 does not respond at all to the high level voltage supplied to the input terminal I.sub.1. Also, this applies similarly to the case in which the other switches 31.sub.2, 31.sub.3, . . . , 31.sub.(n-1), 31.sub.n are in the open state as in the case in which the switch 31.sub.1 is open.
Then, when the state of the switch 31.sub.1 changes from the open state to the closed state, the node of the power supplying resistor 36.sub.1 and the resistor 33.sub.1 is grounded by the closed switch 31.sub.1 causing the cathode voltage of the diode 34.sub.1 plunge from the source voltage of V.sub.cc down almost to the ground voltage. On the other hand, while the source voltage of V.sub.dd is still applied to the anode of the diode 34.sub.1 via the power supplying resistor 37.sub.1, the diode 34.sub.1 is turned to the conducting state due to the plunging-down of the cathode voltage, which lead to the plunging of the anode voltage down to the junction voltage of the diode 34.sub.1 or such a low voltage, for example, as low as nearly 0.6 V. This low voltage causes to shift the input terminal I.sub.1 to the low level voltage state. At this moment the controller 32 performs a control operation corresponding to the function of the switch 31.sub.1 by responding to the change of Voltage from the high level state to the low level state supplied to the input terminal I.sub.1. Also, when the other switches 31.sub.2, 31.sub.3, . . . , 31.sub.(n-1), 31.sub.n change from the open state to the closed state, the controller 32 performs a control operation corresponding to the function of a closed switch 31.sub.2, 31.sub.3, . . . , 31.sub.(n-1), 31.sub.n, similarly as in the case of the closing of the switch 31.sub.1.
When the above stated operations is performed, once the use of the automotive control apparatus or the circuit portion including the switch open-close state-detecting circuit 40 is completed and all of the switches 31.sub.1, 31.sub.2, 31.sub.3, . . . , 31.sub.(n-1), 31.sub.n are kept in the open state longer than a predetermined time, the controller 32 is driven by a sleep setting circuit which is not shown in the drawings to shift the operation mode from the normal mode to the sleep mode with lower power consumption.
Then, when the state of any one of the switches, for example the switch 31.sub.1, is changed from the open state to the closed one in order to use the automotive control apparatus or the circuit portion including the switch open-close state-detecting circuit 40 again, the voltage at the node of the power supplying resistor 36.sub.1 and resistor 33.sub.1 goes down to conduct the diode 34.sub.1 for supplying the low level voltage to the input terminal I.sub.1 as stated above. At this moment a current flows through the detecting resistor 41 in the switch open-close state-detecting circuit 40 to supply the low level voltage to the input terminal of the first inverter 44 due to the voltage drop at the detecting resistor 41 generating a high level voltage at its output terminal, then supplying the high level voltage to the input terminal of the second inverter 45 to generate a low level voltage at its output terminal. Then, in place of the source voltage (high level) of V.sub.dd supplied via the power supplying resistor 47, the low level voltage or an interrupt signal for changing from the high level state to the low level state is applied to the control terminal I.sub.c and the operation mode of the controller 32 returns from the sleep mode to the normal mode to perform a control operation corresponding to the function of the switch 31.sub.1 communicated to the input terminal I.sub.1.
Also, while the controller 32 is in the sleep mode, in case the switch 31.sub.2 is closed in addition to the switch 31.sub.1, the same operation takes place as in the case of closing the switch 31.sub.1 stated above.
As mentioned above, the switch open-close state-detecting circuit 40 detects, in the sleep mode of the controller 32, that the switch 31.sub.1 or the switch 31.sub.2 turned from the open state to the closed state and according to the detected result, it drives the input terminal I.sub.c of the controller 32 with the interrupt signal for changing the high level state to the low level state, the operation mode of the controller 32 returns from the sleep mode to the normal mode. From then on, if any one of the switches 31.sub.1, 31.sub.2, 31.sub.3, . . . , 31.sub.(n-1), 31.sub.n is closed, a control operation is performed corresponding to the function of the closed one.
The above stated known switch open-close state-detecting circuit 40 operates to return the operation mode of the controller 32 from the sleep mode to the normal mode, only when the switch 31.sub.1 or the switch 31.sub.2 is operated from the open state to the closed state to supply the interrupt signal for changing the high level state to the low level state to the input terminal I.sub.c of the controller 32.
However, some kind of switches for an automotive control apparatus has a requirement to have the operation mode of the controller 32 return from the sleep mode to the normal mode, when a switch is operated from the closed state to the open state to supply the interrupt signal for changing from the high level state to the low level state to the input terminal I.sub.c of the controller 32. The known switch open-close state-detecting circuit 40 above stated has a problem that, for such category of switches as above, it cannot supply the desired interrupt signal to the input terminal I.sub.c of the controller 32 and it cannot return the operation mode of the controller 32 from the sleep mode to the normal mode.